19,743 research outputs found
Double-sided coaxial circuit QED with out-of-plane wiring
Superconducting circuits are well established as a strong candidate platform
for the development of quantum computing. In order to advance to a practically
useful level, architectures are needed which combine arrays of many qubits with
selective qubit control and readout, without compromising on coherence. Here we
present a coaxial circuit QED architecture in which qubit and resonator are
fabricated on opposing sides of a single chip, and control and readout wiring
are provided by coaxial wiring running perpendicular to the chip plane. We
present characterisation measurements of a fabricated device in good agreement
with simulated parameters and demonstrating energy relaxation and dephasing
times of s and s respectively. The architecture
allows for scaling to large arrays of selectively controlled and measured
qubits with the advantage of all wiring being out of the plane.Comment: 4 pages, 3 figures, 1 tabl
Circuit quantum acoustodynamics with surface acoustic waves
The experimental investigation of quantum devices incorporating mechanical
resonators has opened up new frontiers in the study of quantum mechanics at a
macroscopic level. Superconducting microwave circuits have proven to be
a powerful platform for the realisation of such quantum devices, both in cavity
optomechanics, and circuit quantum electro-dynamics (QED).
While most experiments to date have involved localised nanomechanical
resonators, it has recently been shown that propagating surface acoustic waves
(SAWs) can be piezoelectrically coupled to superconducting qubits, and
confined in high-quality Fabry-Perot cavities up to microwave frequencies in
the quantum regime, indicating the possibility of realising coherent
exchange of quantum information between the two systems. Here we present
measurements of a device in which a superconducting qubit is embedded in, and
interacts with, the acoustic field of a Fabry-Perot SAW cavity on quartz,
realising a surface acoustic version of cavity quantum electrodynamics. This
quantum acoustodynamics (QAD) architecture may be used to develop new quantum
acoustic devices in which quantum information is stored in trapped on-chip
surface acoustic wavepackets, and manipulated in ways that are impossible with
purely electromagnetic signals, due to the times slower speed of
travel of the mechanical waves.Comment: 12 pages, 9 figures, 1 tabl
HALOGAS observations of NGC 5023 and UGC 2082: Modeling of non-cylindrically symmetric gas distributions in edge-on galaxies
In recent years it has become clear that the vertical structure of disk
galaxies is a key ingredient for understanding galaxy evolution. In particular,
the presence and structure of extra-planar gas has been a focus of research.
The Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) survey aims to provide a
census on the rate of cold neutral gas accretion in nearby galaxies as well as
a statistically significant set of galaxies that can be investigated for their
extra-planar gas properties.
In order to better understand the the vertical structure of the neutral
hydrogen in the two edge-on HALOGAS galaxies NGC 5023 and UGC 2082 we construct
detailed tilted ring models. The addition of distortions resembling arcs or
spiral arms significantly improves the fit of the models to these galaxies. In
the case of UGC 2082 no vertical gradient in rotational velocity is required in
either symmetric models nor non-symmetric models to match the observations. The
best fitting model features two arcs of large vertical extent that may be due
to accretion. In the case of NGC 5023 a vertical gradient is required in
symmetric models (dV/dz = km s kpc) and its
magnitude is significantly lowered when non-symmetric models are considered
(dV/dz = km s kpc). Additionally it is shown that the
underlying disk of NGC 5023 can be made symmetric, in all parameters except the
warp, in non-symmetric models. In comparison to the "classical" modeling these
models fit the data significantly better with a limited addition of free
parameters.Comment: 27 Pages, 22 Figures. Accepted for publication in MNRA
Very High Energy Gamma Rays from PSR1706-44
We have obtained evidence of gamma-ray emission above 1 TeV from PSR1706-44,
using a ground-based telescope of the atmospheric \v{C}erenkov imaging type
located near Woomera, South Australia. This object, a -ray source
discovered by the COS B satellite (2CG342-02), was identified with the radio
pulsar through the discovery of a 102 ms pulsed signal with the EGRET
instrument of the Compton Gamma Ray Observatory. The flux of the present
observation above a threshold of 1 TeV is 1 10
photons cm s, which is two orders of magnitude smaller than the
extrapolation from GeV energies. The analysis is not restricted to a search for
emission modulated with the 102 ms period, and the reported flux is for all
-rays from PSR1706-44, pulsed and unpulsed. The energy output in the
TeV region corresponds to about 10 of the spin down energy loss rate of
the neutron star.Comment: 13 pages, latex format (article), 2 figures include
Detection of Gamma Rays of Up to 50 TeV From the Crab Nebula
Gamma rays with energies greater than 7 TeV from the Crab pulsar/nebula have
been observed at large zenith angles, using the Imaging Atmospheric Technique
from Woomera, South Australia. CANGAROO data taken in 1992, 1993 and 1995
indicate that the energy spectrum extends up to at least 50 TeV, without a
change of the index of the power law spectrum. The observed differential
spectrum is \noindent between 7 TeV and 50 TeV. There is no apparent
cut-off. The spectrum for photon energies above 10 TeV allows the maximum
particle acceleration energy to be inferred, and implies that this unpulsed
emission does not originate near the light cylinder of the pulsar, but in the
nebula where the magnetic field is not strong enough to allow pair creation
from the TeV photons. The hard gamma-ray energy spectrum above 10 TeV also
provides information about the varying role of seed photons for the inverse
Compton process at these high energies, as well as a possible contribution of
-gamma rays from proton collisions.Comment: 19 pages, 4 figures, LaTeX2.09 with AASTeX 4.0 maros, to appear in
Astrophys. J. Let
The X-ray eclipse of the dwarf nova HT CAS observed by the XMM-Newton satellite: spectral and timing analysis
A cataclysmic variable is a binary system consisting of a white dwarf that
accretes material from a secondary object via the Roche-lobe mechanism. In the
case of long enough observation, a detailed temporal analysis can be performed,
allowing the physical properties of the binary system to be determined. We
present an XMM-Newton observation of the dwarf nova HT Cas acquired to resolve
the binary system eclipses and constrain the origin of the X-rays observed. We
also compare our results with previous ROSAT and ASCA data. After the spectral
analysis of the three EPIC camera signals, the observed X-ray light curve was
studied with well known techniques and the eclipse contact points obtained.
The X-ray spectrum can be described by thermal bremsstrahlung of temperature
keV plus a black-body component (upper limit) with
temperature eV. Neglecting the black-body, the bolometric
absorption corrected flux is erg
s cm, which, for a distance of HT Cas of 131 pc, corresponds to a
bolometric luminosity of erg s.
The study of the eclipse in the EPIC light curve permits us to constrain the
size and location of the X-ray emitting region, which turns out to be close to
the white dwarf radius. We measure an X-ray eclipse somewhat smaller (but only
at a level of ) than the corresponding optical one. If this
is the case, we have possibly identified the signature of either high latitude
emission or a layer of X-ray emitting material partially obscured by an
accretion disk.Comment: Accepted for publication on Astronomy and Astrophysics, 200
Analysis of the infinity-replica symmetry breaking solution of the Sherrington-Kirkpatrick model
In this work we analyse the Parisi's infinity-replica symmetry breaking
solution of the Sherrington - Kirkpatrick model without external field using
high order perturbative expansions. The predictions are compared with those
obtained from the numerical solution of the infinity-replica symmetry breaking
equations which are solved using a new pseudo-spectral code which allows for
very accurate results. With this methods we are able to get more insight into
the analytical properties of the solutions. We are also able to determine
numerically the end-point x_{max} of the plateau of q(x) and find that lim_{T
--> 0} x_{max}(T) > 0.5.Comment: 15 pages, 11 figures, RevTeX 4.
- …